Radiolucent retractor and related components

ABSTRACT

A radiolucent halo-type retractor ( 20 ) having a radiolucent curvilinear fixed member ( 32 ) connected to a radiolucent curvilinear movable member ( 34 ). Each of the fixed and movable members has a radiolucent male coupling ( 44, 46 ) projecting outward from a convex surface ( 40, 42 ) to receive a female coupling of a retractor arm. The ends ( 60, 68 ) of the movable member are separated by a distance less than a distance separating the ends ( 56, 64 ) of the fixed member. Radiolucent starburst connectors ( 58, 62 ) are disposed on first ends of the fixed and movable members to secure the fixed and movable members at a desired angular orientation. Radiolucent starburst connectors ( 66, 70 ) are also disposed on second ends of the fixed and movable members to secure the fixed and movable members at a desired angular orientation. A pin ( 72 ) rotatably connects the first ends. A locking shaft ( 76 ) rotatably connects the second ends and is operable to lock the fixed and movable members in a desired orientation.

FIELD OF THE INVENTION

This invention relates generally to the field of surgical instruments,and more particularly, to a halo-style surgical retractor to facilitateholding bodily tissues, membranes, and vessels, retracted during cranialsurgery.

BACKGROUND OF THE INVENTION

There are many different known surgical retractor components, forexample, halo-style retractors and supporting components as well asflexible retractor arms. Halo-style retractors are often made of twohinged, generally semicircular half-rings, a first of which is affixedto supporting structure. A second half-ring is pivotable and adjustablewith respect to the first half-ring about a generally diametric axis ofrotation. Retractor arms and other attachments are attachable to thehalf-rings via an internal dovetail slot extending along an outerdirected surface of the half-rings. The halo-style retractor is mountedon a cranial stabilization device, for example, a skull clamp, and itsposition and orientation are adjustable to meet the needs of thesurgical procedure. Often the skull clamp is radiolucent and may, inturn, be mounted on a radiolucent patient support structure such as anoperating table extension.

The components of such halo-style retractors are usually fabricated fromstainless steel or other metals. One problem with such halo-styleretractors is that the metal is radiopaque to x-ray and other imagingprocesses, and such metal parts produce “artifacts” in resulting images.These artifacts diminish the usefulness of the imaging process becausethey often obscure an image of a portion of a patient that normallywould be viewable, absent the obscuring radiopaque retractor arm,halo-type retractor and supporting components. Further, more and moresurgical procedures are requiring interoperative scanning procedures,and the use of radiopaque retractor components complicates suchprocedures. For example, one option is to remove the radiopaqueequipment prior to the scanning process. As will be appreciated, thatoption is not often possible in an interoperative procedure. Anotheroption is to position and orient the radiopaque retractor components sothat they still provide the desired surgical function but also minimizeartifacts and interference in portions of a scanned image that are ofinterest to a surgeon. This option is at best, difficult, time consumingand provides only a limited benefit, and at worst, the option ispractically not available.

Therefore, there is a need for a radiolucent retractor arm, aradiolucent halo-type surgical retractor and a radiolucent retractorsupport structure that minimize artifacts in an imaging process.

SUMMARY OF THE INVENTION

The present invention provides a radiolucent flexible retractor arm,radiolucent halo-style retractor and radiolucent support structure thatproduce minimal artifacts in an images. The radiolucent retractorcomponents of the present invention are especially beneficial when usedwith interoperative scanning procedures. Further, the radiolucenthalo-style retractor of the present invention uses minimal parts, iscost effective to manufacture and easy to use.

According to the principles of the present invention and in accordancewith the described embodiments, the invention provides a radiolucenthalo-type retractor having a radiolucent curvilinear fixed member and aradiolucent movable member. Each of the fixed and movable members has aradiolucent male coupling projecting radially outward from a convexsurface on the respective fixed and movable members. Further, a pinrotatably connects respective first ends of the fixed and movablemembers; and a locking shaft rotatably connects respective second endsof the fixed and movable members. The locking shaft is operable to lockthe fixed and movable members in a desired relative orientation. Theapplication of male coupling members to the fixed and movable memberssubstantially simplifies the process of molding the fixed and movablemembers and thus, helps to reduce the cost of manufacturing the members.

In another embodiment of the invention, a radiolucent halo-typeretractor has a radiolucent curvilinear fixed member and a radiolucentcurvilinear movable member. First and second radiolucent starburstconnectors are disposed on first ends of the fixed and movable membersrespectively. The first and second starburst connectors secure the firstends of the fixed and movable members at a desired relative angularorientation. Third and fourth radiolucent starburst connectors aredisposed on second ends of the fixed and movable members, respectively.The third and fourth starburst connectors secure the second ends of thefixed and movable members at a desired relative angular orientation. Aradiolucent pin is affixed to one of the first and second starburstconnectors and extends through another of the first and second starburstconnectors. The pin providing an axis of rotation for the first ends ofthe fixed and movable members. A radiolucent locking shaft is mountedwith respect to one of the third and fourth starburst connectors andthreadedly engages another of the third and fourth starburst connectors.The locking shaft provides an axis of rotation for the second ends ofthe fixed and movable members. The use of the four starburst connectorson the overlapping ends of the fixed and movable members simplifies thestructure of the retractor without compromising its rigidity when themembers are locked together.

In a further embodiment of the invention, a radiolucent halo-typeretractor has a radiolucent curvilinear fixed member and a radiolucentcurvilinear movable member. First and second ends of the fixed memberare separated by a distance different from a distance separating firstand second ends of the movable member. A first pin rotatably connectsthe first ends of the fixed and movable members, and a locking shaftrotatably connects the second ends of the fixed and movable members. Thelocking shaft is operable to lock the fixed and movable members in adesired relative orientation.

In one aspect of this invention, the distance separating the ends of themovable member is less than the distance separating the ends of thefixed member. Therefore, upon the locking shaft locking the fixed andmovable members together, the movable member resiliently spreads and thedistance between the first and second ends of the movable member becomessubstantially equal to the distance between the first and the secondends of the fixed member. Such a construction permits the movable memberto be controlled by loosening a single locking shaft. Further, theresiliency of the movable member allows the surgeon to “feel” the motionof the movable member as it “clicks” or “snaps” from one starburst toothto another, and thus, the surgical retractor is substantially easier touse than known halo-style retractors. In addition, the capability ofbeing able to adjust and lock the movable member with respect to thefixed member is accomplished with only one additional part, the lockingshaft. This reduction in parts from known halo-style retractors alsohelps to reduce the manufacturing cost and provides a more reliable andtrouble free operation.

These and other advantageous features of the invention will be morereadily understood in view of the following detailed description of thepreferred embodiment and the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a radiolucent halo-style retractor witha radiolucent support bracket and radiolucent mounting clamp inaccordance with the principles of the present invention.

FIG. 2 is a perspective view of the halo-style retractor arm of FIG. 1without the flexible retractor arm and support bracket.

FIG. 3 is a top plan view of the halo-style retractor shown in FIG. 1with a flexible retractor arm mounted thereon.

FIG. 4 is a cross-sectional view taken along line 4-4 of FIG. 3 andillustrates the mounting of the retractor arm on the halo-styleretractor of FIG. 1.

FIG. 5 is a cross-sectional view taken along the axis of rotation 75 ofFIG. 3 and illustrates one connection between fixed and movable membersof the halo-style retractor of FIG. 1.

FIG. 6 is a cross-sectional view taken along the axis of rotation 75 ofFIG. 3 and illustrates another connection between fixed and movablemembers of the halo-style retractor of FIG. 1.

FIG. 7 is a disassembled view of the support bracket and mounting clampused with the halo-style retractor of FIG. 1.

FIG. 8 is a cross-sectional view taken along line 8-8 of FIG. 3 andillustrates a connection between the support bracket and the halo-styleretractor of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, a radiolucent, halo-style surgical retractor 20 iscomprised of a radiolucent retractor ring 22 that is mounted on upperends of radiolucent support brackets 24, 26. The support brackets are,in turn, mounted at their lower ends to radiolucent mounting clamps 28,30. The retractor ring 22 is comprised of a radiolucent, curvilinearfixed member or half-ring 32 and a radiolucent, curvilinear movablemember or half-ring 34. As shown in FIG. 2, the fixed and movablemembers 32, 34 have respective inner concave surfaces 36, 38 andrespective outer convex surfaces 40, 42. Further, the fixed and movablemembers 32, 34 have respective radiolucent male couplings 44, 46projecting radially outward from the respective convex surfaces 40, 42.The male couplings 44, 46 are substantially identical in constructionand cross-sectional profile.

Referring to FIG. 4, the male coupling 44 has a radiolucent, curvilinearleg 48 with an inner or proximal end connected to the convex surface 40.An outer or distal end of the leg 48 is connected to a radiolucent,curvilinear locking member 50. The male coupling 44 forms curvilinearopposed upper and lower channels 52, 54, respectively. Thus, the malecoupling 44 is capable of receiving a female coupling 55 of a holder 57for a retractor blade or arm 59. The female coupling 55 has respectiveupper and lower projections 61, 63 that extend into the respectivechannels 52, 54, and the female coupling 55 has an internal opening 65that has a cross-sectional profile shaped and sized to slidingly receivethe locking member 50. The holder 57 is secured on the fixed member 32by tightening a locking screw 67 that contacts an outer convex surfaceof the locking member 50. Referring to FIG. 2, each of the lockingmembers 50 of the male couplings 44, 46 have a discontinuity or opening51 that is sized to receive the female coupling 55. The openings 51permit the holder to be mounted on a desired one of the fixed andmovable members 32, 34.

Referring to FIG. 3, the radiolucent fixed member 32 has a first end 56with a radiolucent, first starburst connector 58 disposed thereon.Similarly, the radiolucent movable member 34 has a first end 60 with aradiolucent second starburst connector 62 disposed thereon. Thus, thefirst and second starburst connectors 58, 62 are effective to maintainthe first ends 56, 60 of the respective fixed and movable members 32, 34in a desired angular relationship. The fixed member 32 has a second end64 with a radiolucent third connector 66 disposed thereon, and themovable member 34 has a second end 68 with a radiolucent fourthstarburst connector 70 disposed thereon. Thus, the third and fourthstarburst connectors 66, 70 are effective to maintain the second ends64, 68 of the respective fixed and movable members 32, 34 at a desiredangular orientation with respect to each other.

Referring to FIG. 5, the first end 56 of the fixed member 32 has aradiolucent pin 72 extending therefrom. The pin 72 is disposed at acenter of the first starburst connector 58 and extends through a hole 74located at the center of the second starburst connector 62. Thus, thepin 72 provides an axis of rotation 75 between the first ends 56, 60 ofthe respective fixed and movable members 32, 34.

Referring to FIG. 6, a radiolucent locking shaft 76 extends through aclearance hole 78 located in the center of the third starburst connector66 on the second end 64 of the fixed member 32. The locking shaft 76 hasa threaded end 80 that engages a threaded hole 82 located at the centerof the fourth starburst connector 70 on the second end 68 of the movablemember 34. The locking shaft 76 has a shoulder 84 that contacts ashoulder 86 adjacent the clearance hole 78 so that motion of the lockingshaft 76 through the clearance hole 78 is limited. A radiolucent lockingknob 88 is disposed on an opposite end of the locking shaft 76. As theuser rotates the locking knob 88, the locking shaft 76 pulls the thirdand fourth starburst connectors 66, 70 into engagement. thereby lockingthe second ends 64, 68 of the respective fixed and movable members 32,34 at a desired angular orientation.

Referring back to FIG. 3, in one embodiment, the distance between thefirst and second ends 56, 64 of the first member is different from thedistance between the first and second ends 60, 68 of the movable member34. In other words, the distance between the centers of the first andthird starburst connectors 58, 66 is different from the distance betweenthe centers of the second and fourth starburst connectors 62, 70. Thedistance between the second and fourth starburst connectors 62, 70 isless, for example, by about 0.125 inches, than the distance between thecenters of the first and third starburst connectors 58, 66. Therefore,when the locking shaft 76 is loose, there is a gap or spacing 90 betweenthe third and fourth starburst connectors 66, 70 of about 0.125 inches.As the locking shaft 76 is rotated in a locking direction, the movablemember second end 64 resiliently stretches and moves toward the fixedmember second end 68. That spreading or stretching of the movable member34 brings the fourth starburst connector 70 into locking engagement withthe third starburst connector 66. The spreading or stretching of themovable member 34 also forces the second starburst connector 62 againstthe first. starburst connector 58 via a force vector directed generallyfrom left to right in FIG. 3 and substantially parallel to the axis ofrotation 75.

When the locking shaft 76 is rotated in an opposite, unlockingdirection, movable member 34 automatically returns toward itsunstretched state, that is, its second end 68 automatically moves towardits first end 60. In that process, the movable member second end 68automatically separates from the fixed member second end 64, therebycausing the fourth starburst connector 70 to disengage from the thirdstarburst connector 66. Thus, rotating the locking shaft 76 in theunlocking direction allows the second and fourth starburst connectors62, 70 on the movable member 34 to be rotated with respect to the firstand third starburst connectors 58, 66 on the fixed member 32.

As shown in FIG. 1, the fixed member 32 has first and second radiolucentears 92, 94, respectively, extending radially outward from therespective first and second ends 56, 64. The ears 92, 94 are used tofacilitate attachment of the fixed member 32 with the respectivemounting brackets 24, 26. Since the structure and operation of themounting brackets 24, 26 and clamps 28, 30 are identical, only thestructure and operation of the radiolucent support bracket 24 andradiolucent clamp 28 will be described in detail. The support bracket 24has a radiolucent angular body 96. A radiopaque, metal ball 98 ismounted to an upper end of the body 96. An upper end of a radiolucentsupport rod 100 is rigidly connected to a lower end of the body 96.

Referring to FIGS. 2 and 8, the ear 92 has a generally key-shapedopening 102. The key-shaped opening 102 has a circular portion 104 and aslot portion 106. The circular portion 104 has a diameter larger thanthe diameter of the ball 98, and the slot portion 106 has a slot widthgreater than the diameter of the support rod 100. Thus, the support rod100 with the ball 98 can be readily inserted into the opening 102. Theear 92 further has a threaded opening 108 with a centerline that isoriented substantially perpendicular to a centerline of the opening 102.A radiolucent locking screw 110 threadedly engages the opening 108 andhas an annular end surface 112 that is shaped to tightly contact theball 98 as the locking screw 110 is tightened. Thus, the angularorientation of the fixed member 32 is adjustable by loosening andtightening the radiolucent locking screw 110.

Referring back to FIG. 7, a lower end of the radiolucent support rod 100is attachable to the mounting clamp 28 by extending the support rod 100through a radiolucent compression nut 114 and a radiopaque, metalcompression ball 116 disposed in a radiolucent rod holder 118. Thus, theposition and orientation of the support rod 100 with respect to theclamp 28 is adjustable by tightening and loosening the compression nut114. The rod holder 118 has a radiolucent starburst connector 120 thatis engageable with a radiolucent starburst connector 122 disposed on aradiolucent fixed body 124 of the mounting clamp 28. A radiolucentlocking screw 126 has a threaded end that extends through a clearancehole 128 in the center of the starburst connector 122 and threadedlyengages the rod holder 118. The locking screw 126 has a circular reliefslot 130. Thus, when the locking screw 126 is inserted through theclearance hole 128, the relief slot 130 aligns with a diametricthroughhole 132. A radiolucent retaining pin 134 is inserted through thehole 132 and passes through the relief channel 130, thereby retainingthe locking screw 126 within the fixed body 124. Thus, the angularorientation of the support rod 100 with respect to the mounting clamp 28is adjustable by loosening and tightening the locking screw 126.

The radiolucent fixed body 124 has an opening 136 sized to receive aradiolucent sliding body 138. A radiolucent locking screw 140 has athreaded end that threadedly engages the sliding body 138. The lockingscrew 140 also has a radiolucent retaining pin 142 that extends across acircular relief slot 144, thereby retaining locking screw 140 within thefixed body 124. The fixed body 124 has a radiolucent fixed hook 146 thatis opposite a radiolucent sliding hook 148 on the sliding body 138.Thus, the mounting clamp 28 can be mounted to an arm of a skull clamp bysuccessively loosening and tightening the locking screw 140.

Except as otherwise noted, all of the parts of the halo-style retractor20 are made of a radiolucent material, for example, a “DELRIN” acetalpolymer. Other radiolucent materials may be used. The metal ball 98 andcompression ball 116 are made of aluminum. The various radiolucent partsdescribed herein can be made by machining, by molding, a combination ofmolding or machining or any other process compatible with theradiolucent material.

In use, the radiolucent mounting clamps 28, 30 (FIG. 1) are firstattached to opposite arms of a radiolucent cranial stabilization device,for example, a radiolucent skull clamp (shown in phantom). Such a skullclamp is shown and described in U.S. Pat. No. 5,537,704 that is assignedto the assignee of the present application. Next, the support rods 100of the support brackets 24, 26 are inserted through the rod holders 118of the mounting clamps 28, 30. The retractor ring 22 is located at adesired height with respect to the patient's skull. Next one or moreholders 57 for a retractor arm 59 or other blade holder is placedadjacent to, and slid over, the opening 51 on one of the male couplings44, 46. The retractor arm holder 57 is then moved along the channels orpaths 52, 54 to a desired location and locked in place using lockingscrew 67. The location and angular orientation of the fixed and movablemembers 32, 34 can be further adjusted by loosening and tightening thelocking shaft 76 and locking screws 110.

Referring to FIG. 3, the retractor arm 59 is a disposable, radiolucent,flexible retractor arm and includes a plurality of ball and socketradiolucent pieces, which terminate in a coupling 69 located at an outeror distal end of the retractor arm 59. The coupling 69 is made by ColderProducts Company and is shown in U.S. Pat. No. 5,052,725. This coupling69 enables a retractor blade to be removably held at the distal end ofthe flexible retractor arm 59. Moreover, an internal string (not shown)extends along the entire length of the retractor arm 59; and at itsdistal end, the string is held in place at the coupling 69. At an inneror proximal end of the flexible retractable arm 69, the string is heldin place via a threaded bolt and knob assembly 71, which enables thestring to be tightened or loosened to reorient the position of theretractor arm 59 relative to the halo retractor 20. This enables theflexible retractor arm 59 to be repositioned relative to the head of thepatient, as desired by the neurosurgeon during a neurosurgicalprocedure.

The radiolucent halo-style retractor 20 has several advantages overknown retractors. First, it is radiolucent and substantially reducesartifacts when it is scanned in an imaging process. This is especiallybeneficial when the interoperative scans are taken during a surgicalprocedure. The radiolucent quality of the halo-type retractor, as wellas its shape and connectability with other components, permits it to besecured to a patient within a small volume, or envelope, such thatinteroperative scans of the patient can be taken without disconnectingthe retractor arm, the halo-style retractor or any of the supportingcomponents. Further, substantially all of those components areradiolucent; and therefore, resulting images are almost free of anyartifacts from such equipment.

Second, the application of male coupling members 44, 46 to therespective convex surfaces 40, 42 of the respective fixed and movablemembers 32, 34 substantially simplifies the process of molding the fixedand movable members 32, 34 and thus, helps to reduce the cost ofmanufacturing the members 32, 34.

As earlier described, the movable element has a slightly shorter widthand is resiliently stretched when the locking shaft 76 is tightened.Such a construction permits the movable member to be controlled byloosening a single locking shaft 76. Further, as the locking shaft 76 isloosened, the forces applied on the starburst connectors 58, 62, 66, 60by the resilient movable member 34 permits the movable member to beaccurately adjusted from one tooth on the starbursts to another. Theresiliency of the movable member 34 allows the surgeon to “feel” themotion of the movable member 34 as it “clicks” or “snaps” from onestarburst tooth to another. That feature in combination with the singlelocking shaft 76 makes the surgical retractor 20 substantially easier touse than known halo-style retractors.

In addition, the capability of being able to adjust and lock the movablemember 34 with respect to the fixed member 32 is accomplished with onlyone additional part, the locking shaft 76. This reduction in parts fromknown halo-style retractors also helps to reduce the manufacturing costand provides a more reliable and trouble free operation.

While the invention has been illustrated by the description of oneembodiment and while the embodiment has been described in considerabledetail, there is no intention to restrict nor in any way limit the scopeof the appended claims to such detail. Additional advantages andmodifications will readily appear to those who are skilled in the art.For example, the leg 48 and locking member 50 of FIG. 4 have asubstantially T-shaped cross-sectional profile. As will be appreciated,in other embodiments, the cross-sectional profile of the male couplings44, 46 can have other shapes, for example, an L-shape, a dovetail shape,etc. In another embodiment, the locking member 50 can have a circularcross-sectional profile.

Therefore, the invention in its broadest aspects is not limited to thespecific details shown and described. Consequently, departures may bemade from the details described herein without departing from the spiritand scope of the claims which follow.

1. A radiolucent halo-type retractor comprising: a curvilinear fixedmember comprising first and second ends, and a first radiolucent malecoupling projecting radially outward from the curvilinear fixed memberand adapted to receive a female coupling portion of a retractor arm, thefirst male coupling comprising a first leg member and a first lockingmember, the first leg member extending over a length of the fixed memberand the first leg member comprising an inner end connected to the fixedmember, and a distal end connected to the first locking member; acurvilinear movable member comprising first and second ends, and asecond male coupling projecting radially outward from the curvilinearmovable member and adapted to receive a female coupling of a retractorarm, the second male coupling comprising a second leg member and asecond locking member, the second leg member extending over a length ofthe movable member and the second leg member comprising an inner endconnected to the movable member and a distal end connected to the secondlocking member; a first pin rotatably connecting fixed in one of thefirst ends and the second ends extending into an other of the first endsto rotatably connect the first ends together; and a locking shaftrotatably connecting another of the first ends and extending through oneof the second ends and threaded into an other of the second ends, thelocking shaft operable to lock the fixed and movable members in adesired relative orientation.
 2. A radiolucent halo-type retractorcomprising: a radiolucent curvilinear fixed member comprising first andsecond ends, a first convex surface, and a first radiolucent malecoupling projecting outward from the first convex surface and adapted toreceive a female coupling portion of a retractor arm, the firstradiolucent male coupling comprising a first leg member and a firstlocking member, the first leg member extending over a length of thefirst convex surface and the first leg member comprising an inner endfixed to the first convex surface and a distal end connected to thefirst locking member; a radiolucent curvilinear movable membercomprising first and second ends, a second convex surface, and a secondradiolucent male coupling projecting outward from the second convexsurface of the movable member, the second radiolucent male couplingcomprising a second leg member and a second locking member, the secondleg member extending over a length of the second convex surface and thesecond leg member comprising an inner end fixed to the second convexsurface and a distal end connected to the second locking member; a firstpin fixed to one of the first ends and extending into an other of thefirst ends to rotatably connect the first ends together; and a lockingshaft rotatably connecting another of the first ends and extendingthrough one of the second ends and threaded into an other of the secondends, the locking shaft operable to lock the fixed and movable membersin a desired relative orientation.
 3. The radiolucent halo-typeretractor of claim 2 wherein each of the first and the secondradiolucent male couplings forms a channel with a respective one of theconvex surfaces.
 4. The radiolucent halo-type retractor of claim 2wherein each of the first and the second radiolucent male couplingsforms a pair of opposed channels with a respective one of the convexsurfaces.
 5. The radiolucent halo-type retractor of claim 2 wherein eachof the first and the second radiolucent male couplings comprises asubstantially T-shaped cross-sectional profile.
 6. The radiolucenthalo-type retractor of claim 2 wherein each of the first and secondradiolucent male couplings comprises a substantially L-shapedcross-sectional profile.
 7. The radiolucent halo-type retractor of claim6 wherein each of the leg members and each respective locking memberforms a channel with a respective one of the convex surfaces.
 8. Theradiolucent halo-type retractor of claim 7 wherein each of the legmembers and the a respective locking member form a substantiallyT-shaped coupling.
 9. The radiolucent halo-type retractor of claim 8wherein each leg member and a respective locking member form a pair ofchannels with a respective one of the convex surfaces.
 10. Theradiolucent halo-type retractor of claim 2 wherein the locking shaft ismade from a radiolucent material.
 11. The radiolucent halo-typeretractor of claim 2 wherein the pin is made from a radiolucentmaterial.
 12. The radiolucent halo-type retractor of claim 2 wherein thefixed and movable members are substantially semicircular.
 13. Theradiolucent halo-type retractor of claim 2 further comprising aradiolucent retractor arm having a radiolucent female couplingconnectable to one of the first and the second male couplings.
 14. Aradiolucent halo-type retractor comprising: a radiolucent curvilinearfixed member comprising first and second ends; a radiolucent curvilinearmovable member comprising first and second ends; first and secondradiolucent starburst connectors disposed on the first ends of the fixedand movable members, respectively, the first and second starburstconnectors securing the first ends of the fixed and movable members at adesired relative angular orientation; third and fourth radiolucentstarburst connectors disposed on the second ends of the fixed andmovable members, respectively, the third and fourth starburst connectorssecuring the second ends of the fixed and movable members at a desiredrelative angular orientation; a radiolucent pin affixed to one of thefirst and second starburst connectors and extending through another ofthe first and second starburst connectors, the pin providing an axis ofrotation for the first ends of the fixed and movable members; and aradiolucent locking shaft mounted with respect to one of the third andfourth starburst connectors and threadedly engaging another of the thirdand fourth starburst connectors, the locking shaft providing an axis ofrotation for the second ends of the fixed and movable members.
 15. Theradiolucent halo-type retractor of claim 14 wherein each of the fixedand movable members has respective opposed convex and concave surfaces,and the first starburst connector is disposed on the concave surface ofthe fixed member and the second starburst is disposed on the convexsurface of the movable member.
 16. The radiolucent halo-type retractorof claim 15 wherein the third starburst connector is disposed on theconvex surface of the fixed member and the fourth starburst is disposedon the concave surface of the movable member.
 17. The radiolucenthalo-type retractor of claim 16 wherein the radiolucent locking shaft ismounted with respect to the first starburst connectors on the fixedmember and threadedly engages the second starburst connector on themovable member.
 18. The radiolucent halo-type retractor of claim 17wherein the radiolucent pin is affixed to the third starburst connectoron the fixed member and extends through the fourth starburst connector.19. The radiolucent halo-type retractor of claim 14 further comprising aradiolucent retractor arm connectable to one of the fixed and themovable members.
 20. A radiolucent halo-type retractor comprising: aradiolucent curvilinear fixed member comprising first and second ends,and a first convex surface, a radiolucent curvilinear movable membercomprising first and second ends, and a second convex surface, the firstand second ends of the fixed member being separated by a distancedifferent from a distance separating the first and second ends of themovable member; a first pin rotatably connecting one of the first endsand the second ends; and a locking shaft rotatably connecting another ofthe first ends and the second ends, the locking shaft operable to lockthe fixed and movable members in a desired relative orientation and uponthe locking shaft locking the fixed and movable members together, thedistance between the first and second ends of the fixed member becomingequal to the distance between the first and the second ends of themovable member and the first and second ends of one of the fixed memberand the movable member resiliently spreading apart.
 21. The radiolucenthalo-type retractor of claim 20 wherein the first and second ends of thefixed member are separated by a distance greater than the distanceseparating the first and the second ends of the movable member.
 22. Theradiolucent halo-type retractor of claim 21 wherein the first and secondends of the movable member resiliently spread apart as the lockingmember locks the fixed and the movable members together.
 23. Theradiolucent halo-type retractor of claim 22 wherein the first and secondends of the movable member automatically move toward each other as thelocking member loosens the fixed and the movable members.
 24. Theradiolucent halo-type retractor of claim 23 further comprising first andsecond radiolucent starburst connectors disposed on the first ends ofthe fixed and movable members, respectively, the first and secondstarburst connectors securing the first ends of the fixed and movablemembers at a desired relative angular orientation in response to thelocking shaft locking the fixed and movable members together.
 25. Theradiolucent halo-type retractor of claim 24 wherein the first and secondends of the movable member automatically move toward each other as thelocking member loosens the fixed and the movable members, the motion ofthe first and the second ends of the movable member permits the firstand the second starburst connectors to be moved relative to each other.26. The radiolucent halo-type retractor of claim 25 further comprisingthird and fourth radiolucent starburst connectors disposed on the secondends of the fixed and movable members, respectively, the third andfourth starburst connectors securing the second ends of the fixed andmovable members at a desired relative angular orientation in response tothe locking shaft locking the fixed and movable members together. 27.The radiolucent halo-type retractor of claim 26 wherein the first andsecond ends of the movable member automatically move toward each otheras the locking member loosens the fixed and the movable members, themotion of the first and the second ends of the movable member permitsthe third and the fourth starburst connectors to be moved relative toeach other.
 28. A halo-type retractor comprising: a curvilinear fixedmember; a curvilinear movable member connected to, and movable withrespect to, the fixed member; a support bracket connectable to the fixedmember, the support bracket having a radiolucent support rod; a mountingclamp comprising a rod holder connectable to the support rod, aradiolucent fixed body having a first hook and being connectable to therod holder, a movable body having a second hook, the movable body beingmounted for linear motion in, and securable relative to, the fixed body,the movable body and the second hook being translatable along a linearpath toward and away from the first hook and adapted to respectivelyclamp and unclamp the halo-type retractor with respect to a cranialstabilization device.
 29. A radiolucent halo-type retractor comprising:a radiolucent curvilinear fixed member comprising first and second ends,a first convex surface, and a first radiolucent male coupling projectingoutward from the first convex surface and adapted to receive a femalecoupling portion of a retractor arm; a radiolucent curvilinear movablemember comprising first and second ends, a second convex surface, and asecond radiolucent male coupling projecting outward from the secondconvex surface of the movable member and adapted to receive a femalecoupling of a retractor arm, the first and second ends of the fixedmember being separated by a distance different from a distanceseparating the first and second ends of the movable member; first andsecond radiolucent starburst connectors disposed on the first ends ofthe fixed and movable members, respectively, the first and secondstarburst connectors securing the first ends of the fixed and movablemembers at a desired relative angular orientation; third and fourthradiolucent starburst connectors disposed on the second ends of thefixed and movable members, respectively, the third and fourth starburstconnectors securing the second ends of the fixed and movable members ata desired relative angular orientation; a first pin rotatably connectingthe first ends; and a locking shaft rotatably connecting the secondends, the locking shaft operable to lock the fixed and movable membersin a desired relative orientation.
 30. The halo-type retractor of claim28 wherein the fixed member, the movable member, the support bracket andthe mounting clamp are substantially radiolucent.
 31. (new) A mountingclamp for connecting a support rod to a cranial stabilization device,the support rod having an upper end connected to a surgical toolsupport, the mounting clamp comprising: a rod holder adapted to besecured to the support rod at desired locations along a length of thesupport rod; a fixed body having a first hook and connectable the rodholder; and a movable body having a second hook, the movable body beingmounted for linear motion in, and securable relative to, the fixed body,the movable body and the second hook being translatable along a linearpath toward and away from the first hook and adapted to respectivelyclamp and unclamp the support rod to the cranial stabilization device.32. The halo-type retractor of claim 31 wherein the rod holder, thefixed body and the movable body are substantially radiolucent.
 33. Ahalo-type retractor comprising: a curvilinear fixed member comprising afirst cavity disposed in a first surface of the fixed member, a secondcavity disposed in another surface of the fixed member, the secondcavity intersecting with, and being substantially perpendicular to, thefirst cavity, and a locking screw threaded into the fixed member andhaving a distal end; a curvilinear movable member connected to, andmovable with respect to, the fixed member; a support bracket connectableto the fixed member, the support bracket comprising a support rod beingslidable through the second cavity, and a projection on an upper end ofthe support rod, the projection being slidable through the first cavitybut not through the second cavity, the projection being lockable in thesecond cavity by rotation of the locking screw; and a mounting clampadapted to clamp and unclamp the halo-type retractor with respect to acranial stabilization device.
 34. The halo-type retractor of claim 33further comprising: a third cavity disposed in a third surface of thecurvilinear fixed member at a location substantially diametricallyopposed a location of the first cavity; a fourth cavity disposed in afourth surface of the fixed member, the third cavity intersecting with,and being substantially perpendicular to, the fourth cavity; and asecond locking screw threaded into the fixed member and having a distalend.
 35. A surgical tool support mountable on a ball end of a supportrod, the ball end having a diameter larger than a diameter of thesupport rod, the surgical tool support comprising: a member adapted tosupport a surgical tool, the member having an opening comprising acircular portion disposed above and intersecting a slot portion, thecircular portion having a diameter larger than a width of the slotportion, the circular portion adapted to receive a ball end of a supportrod being slid therethrough and the slot portion adapted to receive thesupport rod being slid therethrough, the slot portion being sized not toreceive the ball portion of the support rod; and a locking screwthreaded into the member and having a distal end extending into thecircular portion of the opening, the ball portion of the support rodbeing lockable in the circular portion of the opening by rotation of thelocking screw.
 36. The surgical tool support of claim 35 wherein thelocking screw has a longitudinal centerline substantially collinear witha longitudinal centerline with the slot portion of the opening.
 37. Thesurgical tool support of claim 35 wherein the member and the lockingscrew are substantially radiolucent.